Escutcheon design for circuit breakers



Nov. 13, 1956 c. J. YARRlcK 2,770,701

ESCUTCHEON DESIGN FOR CIRCUIT BREAKERS Filed Oct. 29, 1951 5 Sheets-Sheet l INVEN T R. fi'xlmut; J. nee/ex Nov. 13, 1956 c. J. YARRICK 2,770,701

ESCUTCHEON DESIGN FOR CIRCUIT BREAKERS Filed Oct, 29, 1951 5 Sheets-Sheet 2 INVENTOR. 67/4445; J. Mme/ax T15. 5' BY c. J. YARRICK 2,770,701

ESCUTCHEON DESIGN FOR CIRCUIT BREAKERS 5'Sheets-Sheet 3 Nov. 13, 1956 Filed Oct. 29, 1951 JNVENTOR.

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Nov. 13, 1956 c. J. YARRICK ESCUTCHEON DESIGN FOR CIRCUIT BREAKERS 5 Sheets-Sheet 4 Filed Oct. 29, 1951 INVENTOR. /IAWMEJ v! lien/ca.

Nov. 13, 1956 c. J. YARRICK 2,770,701

ESCUTCHEON DESIGN FOR CIRCUIT BREAKERS Filed Oct. 29, 1951 5 Sheets-Sheet 5 IN V EN TOR.

United States Patent ESCUTCHEON DESIGN FOR CIRCUIT BREAKERS Charles J. Yarrick, West Collingswood, N. J., assignor to I-T-E Circuit Breaker Company, Philadelphia, Pa., a corporation of Pennsylvania Application October 29, 1951, Serial No. 253,717

7 Claims. (Cl. 200-167) The present invention relates to circuit breakers and more particularly to an escutcheon unit for use therewith.

The interruption of high current involving relatively large amounts if power is a hazardous task to personnel and connected equipment unless it is performed under carefully defined conditions. The operator may be injured or killed by the failure of any one of several components of the breaker. Equipment may be extensively damaged by failure of the circuit breaker to properly perform its function.

Essentially, the novel safety features incorporated in the circuit breaker are in the escutcheon, the operating mechanism, the control relay and the arc chute. The combination of the novel operating features as incorporated in the circuit breaker and as described in the present application provide a very safe interrupter for high currents.

It is then a primary object of the present invention to provide a novel and highly safe circuit breaker.

Another object of this invention is the arrangement and construction of a circuit breaker in such manner that each of the parts thereof embraced in individual unit assemblies may readily be interchanged with similar unit assemblies of other circuit breakers so that the circuit breaker construction as a whole is particularly adapted to mass production methods and procedures.

A further object of the present invention is the provision of novel operating means for closing and tripping the circuit breaker.

A further object of the present invention is the provision of a novel self-sealing escutcheon upon increase of gas pressure interior to the circuit breaker.

The foregoing and many other objects of the present invention will become clear from the following description and the accompanying drawings, in Which- Figure 1 is a front view of the novel circuit breaker of the present invention with the front panel removed.

Figure 2 is a side view of the novel circuit breaker of the present invention.

Figure 3 is a cross-sectional side view of the novel circuit breaker with the contacts open.

Figure 4 is a sectional view of part of the operating mechanism along line 4-4 in Figure 3.

Figure 5 is a sectional view along line 5-5 in Figure 3 of a portion of the operating mechanism of the circuit breaker of the present invention.

Figure 6 is arpartial side cross-sectional view of the novel circuit breaker of the present invention with the contacts closed. I

Figure 7 is an exploded view in perspective of the operating mechanism of the novel circuit breaker of the present invention.

Figure 8 is a front view of the novel escutcheon of the present invention in the open position.

Figure 9 is a front view of the novel escutcheon of the present invention in the closed position. 1

2,770,701 Patented Nov. 13, 1956 Figure 10 is a sectional view along lines 14-14 in Figure 8.

Figure 11 is a sectional view along 15-15 in Figure 9.

Referring now to Figures 1 and 2, there is here shown a circuit breaker 30 with my novel escutcheon unit of my present invention. Circuit breaker 30 is composed of a plurality of unit assemblies which include the contact structure 31, the arc shute assemblies 32, the operating mechanism 33, control assembly 34, the escutcheon mounting assembly 35 and the trip unit 36.

The circuit breaker 30 as shown in these figures is a three pole circuit breaker in which three contact structures 31 and three are shute assemblies 32 are provided. The contact structures 31 are provided with three stationary contacts and three movable contacts, as hereinafter described. One control assembly 34 is provided for the circuit breaker 30, the unit operating a plunger to close a circuit breaker. A single operating mechanism 33 is, however, provided which is used to close and open the circuit breaker contacts. The circuit breaker 30 is supported on a steel panel 40 a portion of which is shown more specifically in Figure 9.

The panel 40 is a flat steel plate provided with three openings 41. The three openings 41 are aligned horizontally adjacent the upper end of the steel panel 40 and are square shaped. The said openings 41 are provided to receive part of the base mouldings.

Under overcurrent condition, shown dotted in Figure 3, an energized coil 139 aided by a core 141 pulls an armature 142 against itself. The armature 142 comprises two units 143, seen also in Figure 7. The units 143 each have a screw threaded at one end thereof and which is used to effect an adjustable contact with the initial tripping member 140. The head 144 of the screw 145 acts to rotate bar 140 upon the energizing of the coil 139 and hits extension plate 146 which is bolted to the shaft 140 described above. When the head 144 hits the end of the extension plate 146, the shaft 140 is caused to rotate in a counterclockwise manner looking from the right of the circuit breaker 30, which is the view of Figure 7.

The shaft 140 is also caused to rotate by means of a coil 150 which upon being energized pulls an armature member 151 to it. The member 151 has a link 152 rigidly attached to one end 153 of member 151 by means of an angle 154. The link 152 is attached to the angle 154 by means of a threaded portion 19 of link 152 which enters the angle 154 and a nut 148. The angle 154 is movably attached to the member 151 by means of a pin 155. A restoring spring 147 attached to the member 151 resets the armature upon de-energization of the coil 150.

The'link 152 is attached to the shaft 140 by means of another angle 156. The angle 156 is attached to the shaft 140 by means of two bolts 15S and to the link 152 by means of a cap 160. The cap 160 is movably attached to the link 152. Thus, the shaft 140 can now be caused to rotate by two methods, one due to the energization of the overcurrent trip coil 139 and the other due to the energizing of the coil 150. The coil 150 is remotely caused to be energized and is usually accomplished by manual operation. of a remote pushbutton switch. The rotation of shaft 140 causes a link 162 to be moved by means of an angle 163 which is bolted to the shaft 141 by means of two bolts 163. The angle 163 has an indentation 165 near the farthest edge 166 from the shaft 140. The link 162 has two slots 168 and 167. The slot 167 engages the indentation 165 of angle 163'.

The translatory movement of link 162 causes the rotation of a milled shaft 170. The milled shaft 170 has another angle 171 rigidly attached to it by means of two bolts 172. This angle has an indentation 173 near the end 174 which is farthest from the shaft 170. The

indentation 173 of angle 171 engages the slot 168 of link 162. Thus the rotation of shaft 140 causes the rotation of milled shaft 170.

When milled shaft 170 rotates to release a latch 177, as is hereinafter described, the circuit breaker movable contacts are allowed to be disengaged from the stationary contacts.

The angle 171 described above has an abutment 178. This abutment 178 is engaged by a roller 179 which is rotated manually by means of the closing handle 184 attached to the shaft 180. Shaft 180 has a crank 181 which is rigidly attached to the shaft 180 by means of a screw 182. The roller 179 is attached to one end of the crank 171. closing handle 184 the roller 179 engages abutment 178 of angle 171 and rotated milled shaft 170. Thus milled shaft 170 can be made to rotate by a plurality of methods. It can be made to rotate manually by means of closing handle 184; it can be made to rotate by means of an overcurrent condition in coil 139, as described above; and it can be made to rotate by means of an excitation of coil 150, as described above.

The latch 177 is an integral part of trip arm 185. The latch 177 engages themilled shaft 170 so that a small revolution of shaft 170 releases the latch 177, as hereinafter described. The shaft 170 is milled slightly past center at 186. The trip arm 185 is pivoted at 187 on a long pin 188. The pin 188 is also engaged on the trip arm extension 187 at point 183. The pin 188 carries a movable arm 190. The movable arm 190 is pivoted on pin 188 at points 191 and 192 and extends beneath a roller 193. The roller 193 is the pivot point of a toggle mechanism consisting of two links 194 and 195 and is carried by a pin 202 which pivots the meeting of links 194 and 195.

The links 194 and 195 each comprise two arms, 194A and 194B, and 195A and 195B, respectively. Arms 194A and 194B are pivoted on floating pin 196 described above and arms 195A and 19513 are pivoted on pin 204 also described above.

The arms 194A and 1943 support a rod 197 at 198 and 199, respectively. The rod 197 carries one end of a restoring spring 203 which is tensed by means of a stationary shaft 212, hereinafter described. The restoring spring 203 exerts a tension on the link 194 which tends to open or break the toggle mechanism. Link 194 is pivoted on a floating pin 196, which is supported by link arm 185 and its extension 189 being parallel to the pin 188. The other link 195 of the toggle is pivoted on movable link 200 which is connected by means of an adjustable insulator 201 to the movable contact assembly 61 described above. When the toggle mechanism consisting of links 194 and 195 is straightened out by means hereinafter described, pressure is put on movable link 200 by means of link 195 and bearing pin 204. The movable link 200 is pinned to insulator 201 by a pin 205 and moves so as to advance the insulator 201 and the movable contacts 61 towards the stationary contact 60.

in the exploded view shown in Figure 7 the contacts are open and the toggle mechanism consisting of links 194 and is collapsed. The circuit breaker may be closed by a variety of methods. The circuit can be closed manually by means of shaft 180 rotated by closing handie 184 described above. If shaft 180 is rotated in the direction indicated by the arrow 184A, the roller 179 will engage the bottom of arm 190 and force the arm 190 against roller 193, thus straightening out the toggle mechanism and closing the circuit breaker contacts.

The movable links 200 are under an opening tension by means of opening spring 210 so that if no additional locking action other than described above for supporting the toggle existed, the circuit breaker would re-open immediately upon releasing the shaft 180. The locking device is supplied by means of a crank 211 which is When the shaft 180 is rotated by the I located on a shaft 212 mentioned above, whose longitudinal axis is parallel to the axis of the milled shaft 170 and the rod 140. The crank 211 has two arms 213 and 214. The arm 213 is located, when the circuit breaker is open, adjacent the roller 193. When the roller 193 is forced upward, as due to the pressure of arm 190, the roller pushes against arm 213 of crank 211, rotating the crank 211 slightly on shaft 212. When the roller 193 has cleared the top of arm 213, the arm 213 snaps underneath the roller 193 due to the compression of a spring 220. The spring 220 which is wound on the shaft 212 has one end in an indentation 221 of crank 211 and the other end borne against a shaft 222 which pierces the trip arm 185. The shafts 212 and 222 have been moved out of position in the exploded view for the sake of clarity. Actually the shaft 222 pierces the trip arm 185 at point 207. The longitudinal axis of shaft 222 is essentially parallel to the longitudinal axis of shaft 212 and milled shaft 170.

When the roller 193 is moved, straightening the toggle, it causes crank 211 to rotate compressing spring 220. The roller clears the top of arm 213 letting the crank rotate in the opposite direction until the arm 213 is directly beneath and supporting the roller 193. The other arm 214 or crank 211 bears against the shaft 222 preventing further rotation of the crank 211 so that the arm 213 is stopped directly beneath the roller 193. The spring 220 is under compression normally so that the arm 214 is constantly bearing against the shaft 222. When the toggle is straightened, the rotation of the crank 211 moves the arm 214 away from the shaft 222 until the roller 193 clears the top of arm 213. Then the reverse rotation of the crank 211 occurs until the arm 214 again bears against shaft 212.

Thus, when the toggle is straightened and the circuit breaker closed, the crank 211 lock the toggle and thus locks the circuit breaker in a closed position.

The closing handle 184 by means of the shaft 180, after closing the circuit breaker by means of the rotation of roller 179 against the arm 190, as described above, is returned to its normal position by means of a crank 230. The crank 230 is pivoted on a stationary pin 231.

The crank 181 described above has an indentation 232 which meets a roller 233 of crank 230. The crank 230 supports a pin 234 which has a restraining spring 235 engaged at one end 236. The restraining spring 235 is attached to an angle 237 and is tensed on the pin 236, causing the crank 230 to rotate. The rotation of crank 230 causes the roller 233 to meet the indentation 232 returning the crank 181 to its normal position.

The circuit breaker may also be closed by means of a plunger 240 shown alsoin Figures 3 and 5. The plunger 240 is part of the core of a solenoid coil 241. A remote signal energizes the coil 241 and causes the plunger extension 240 to push against the roller 193 in a similar manner as the arm 190. The roller 193 is a cylinder and has the arm meet it on one-half and the plunger extension 240 meet it at the other half. The plunger extension 240 raises the roller 193 straightening out the toggle mechanism and closing the circuit breaker with the locking action due to crank 211 similarly as described in reference to the manual closing of the circuit breaker.

The closing solenoid 241 is energized from a remote point in the following manner.

When the circuit breaker is desired to be closed from a remote point, a button is depressed which energizes the relay coil 300. The energized coil 300 acts as an electromagnetand attracts the-movable armature 301 shown in Figure 8.. The movable member 301 is pivoted in three places by pins 302, 303, and 304. The pin.302 is a fixed pivot but the other two pins, 303 and 304, are floating pivots. The pin 302 also supports an extension 305 of ,amovable bracket 306. The extension 305 is The bracket 306 carries at one end the extension 305 and at the other end a V-shaped contact 308. The contact 308 is movably connected to bracket 306 by means of two pins 309. The pins 309 are movable with respect to the bracket 306 and the contact 307. The bracket 306 and the contact 308 are held together by means of the springs 310 supported against the top of the pins 309. The contracted springs 310 force the contact 308 against the bracket 306. I

The movable member 301 has alaminated armature 312. The laminated armature 312 is rigidly attached to the member 301 by means of force fit pins 313 and 314. The movable member 301 has also as an integral part thereof an angle, not shown, which bears a dielectric rectangular strip 315.

When the coil 300 is energized, the bracket 306 brought closer to the coil 300 making strip 315 just touch a contact 316, shown in Figure 2.

Once coil 300 is energized, the movable member 301 carrying the bracket 306 is locked against coil 300, as is hereinafter described, obviating the further energization of coil 300. Thus, touching the remote button, not shown, but briefly, is sufficient to lock the mechanism described against'the coil 300. Y 1

When coil 300 is energized, it energizes in turn closing solenoid coil 241 describedabove, causing the plunger extension 240 to move against the roller 193. The plunger extension 240 carries at its'dista'l end a crosssectionally square core 320 which slides into opening member 322. As the plunger completes the closing of the circuit breaker by means of pushing roller 193 onto arm 213, as described above, the member 329 engages the head 323 of a screw 324. The screw 324 is carried by a link 326, which is pivoted by a floating pin 304 of the movable member 301.

The link 325 normally rests against a pin 326 carried at one end of a tray-like member 327. The member 327 is pivoted at its other end on a floating pin 328 which also pivots the end of the extension 305 described above. Pin 303 and pin 328 carry springs not shown which are tensed to pin 326.

The control relay, as described above, maintains the relay contact 308 in a substantially latched position with the armature 301 under normal conditions. Upon energization of the coil 300, the armature 301 moves to its closed position carrying the contact 308 with it. The engagement of the movable relay contact 308 with the stationary relay contacts 502 shown in Figure 8 establishes the circuit of the closing solenoid.

When the head 323 is hit by member 322 the mechanism shifts, causing the opening of the circuit deactivating coils 300 and 241. The closing solenoid plunger 240 will open the latch engagement between the relay armature 307 and the relay contacts 308 when the closing solenoid plunger 240 nears its completion of the closing stroke. This allows the closing solenoid 300' electrical circuit to be interrupted when the circuit breaker 30 is securely latched in the closed position. As long as the relay operating switch is held in the closed position, the relay operating coil 300 will hold the relay armature 301 in sealed position while the relay contacts 308 remain in the open position. The relay armature 301 and the relay contacts 308 cannot relatch until the relay closing switch is released. This operating characteristic makes the relay trip free. Continuous pumping of the circuit breaker closing mechanism is thus prevented using a maintained contact close switch under conditions when a fault remains on the circuit or where defective closing mechanism causes defective latching.

An external indication as to whether the circuit breaker 30 is open or closed is provided above the closing handle 184 by means of visual indicator 400 shown in Figures 3, 6, 8, 9 and 24. The visual indicator 400 is directly driven as is hereafter described by the movement of the links 200 described above which moves whenever the circuit breaker 30 opens or closes.

escutcheon 425. The escutcheon 425 and the handle 184 Referring now to Figures 3 and 6, the end 401 of the link 200 has two holes 402. The link 200 by means of the screws 403 and the nuts 404 through the holes 402 support the plates 405. The link 200 rotates on the bar 406 which is partially rectangular and partially circular in cross sectioned shape. The rectangular cross-sectional shape of the bar 406 passes through the opening 407 in the link 200 and circular portion of the bar 406 is supported on the housing 408 of the circuit breaker 30. Thus, the bar 406 rotates easily in its support on the housing 408 carrying with it the links 200 without any slippage.

The plate 405 carries a pin 409 which moves essentially up or down dependent upon whether the circuit breaker is opening or closing, respectively. The pin 409 engages a link 410 through the opening 411. The link 410 carries a pin 412 at its other end which is supported on a sliding member 413. Sliding member 413 has attached to it a spring 414. The other end of the spring 414 is attached to the indicator-carrier 415. The carrier 415 has the two words Open and Closed thereon; the word Open being indicated at 416' and the word Closed at 417. The other end of the indicator-carrier 415 is provided with a notch 416 which pivots on the pin 417. The movement of the words Open and Closed at '416 and 417' is then a circular motion. The front face 418 is spherically shaped. The spherical shape of the face 418 allows good visibility from the sides, top and bottom.

The visual design as described above is directly driven through the links 200, the arms 405, the link 410, and the sliding member 413 and is thus independent of operation by means of a spring whose failure is the usual cause of a false indication.

The closing handle 184 is provided with a locking bar 420 shown particularly in Figures 3 and 10. The top of the handle 184 is slotted at 421 to receive the locking bar 420 pivotally mounted upon the pin 603. A suitable spring may be provided if so desired to bias the locking bar 420.

The present modification operates the bar 420 gravitationally so that the locking tip 423 presses against the circular platform 424 of the escutcheon plate 425. The platform 424 has a notch or slot 427 shown in Figures 10 and 11.

Rotation of the closing handle 184 in a counterclockwise direction with respect to Figures 8 and 9 will cause the locking bar 420 to be rotated to such a position that the locking tip 423 Will enter the notch 427.

As long as the tip 423 is seated in the notch 427, the

circuit breaker 30 cannot be closed. The locking bar 420 is provided with a slot 428 having a sufiicient width to permit the passing of a hasp of a padlock 430 (Figure 10) therethrough. This is an important safety factor in the use of the present circuit breaker as unauthorized personnel are thus restrained from closing the breaker.

The handle 184 is seated against the circular portion 424 described above which is an integral part of the are the only portions of the circuit breaker which can be viewed by the operator. The escutcheon has a self-aligning plate 431 As shown particularly in Figure 11, the plate 431 is aligned by means of two springs 432 which are coiled on the sliding pins 433. The pins 433 are fixed to the plate 431 at 434 and slide through the bars 435. The bars 435 are held rigidly in place against the back of the escutcheon 425 by means of screws 437.

The escutcheon plate 431 is then self-aligning in that any reasonable deviation in its alignment with the front hinged enclosure 440, shown in Figures 3 and 6, is automatically compensated for by the design. The design provides a safety factor in that gas pressures originated inside the circuit breaker enclosure tend to establish a sealing effect by forcing the escutcheon plate 431 against '7 the cover 440 and thus preventing exposure of the operator to dangerous flare-ups.

In the foregoing the invention has been described solely in connection with specific illustrative embodiments thereof. Since many variations and modifications of the invention will now be obvious to those skilled in the art, it is preferred to be bound not by the specific disclosures herein contained but only by the appended claims.

I claim:

1. An escutcheon unit for circuit breakers comprising a movable gas-excluding rigid escutcheon plate, a stationary escutcheon plate, a visual indicator, a handle and a driving mechanism; said visual indicator being moved by said driving mechanism when said circuit breaker is opened or closed; said stationary escutcheon plate being fixed with respect to said circuit breaker and having movably mounted thereon said handle which manually operates said circuit breaker; resilient means pressing said movable escutcheon plate into sealing relationship with said stationary escutcheon plate.

2. An escutcheon unit for circuit breakers comprising a movable gas-excluding rigid escutcheon plate, a stationary escutcheon plate, a visual indicator, a handle and a driving mechanism; said visual indicator being moved by said driving mechanism when said circuit breaker is opened or closed; said stationary escutcheon plate being fixed with respect to said circuit breaker and having movably mounted thereon said handle which manually operates said circuit breaker; resilient means pressing said movable escutcheon plate into sealing relationship with said stationary escutcheon plate; said stationary escutcheon plate having a cylindrical platform for seating said handle and a spherical protrusion having an opening permitting visual access to said visual indicator.

3. An escutcheon unit for circuit breakers comprising a movable gas-excluding rigid escutcheon plate, a stationary escutcheon plate, a visual indicator, a handle and a driving mechanism; said visual indicator being moved by said driving mechanism when said circuit breaker is opened or closed; said stationary escutcheon plate being fixed with respect to said circuit breaker and having movably mounted thereon said handle which manually operates said circuit breaker; biasing means urging said movable escutcheon plate into sealing relationship with said stationary escutcheon plate; said visual indicator having an indication at one end and being pivoted at the other end thereof so that said indication moves in a circular path.

4. An escutcheon unit for circuit breakers comprising a movable gas-excluding rigid escutcheon plate, a stationary escutcheon plate, a visual indicator, a handle and a driving mechanism; said visual indicator being moved by said driving mechanism when said circuit breaker is opened or closed; said stationary escutcheon plate being fixed with respect to said circuit breaker and having movably mounted thereon said handle which manually operates said circuit breaker; a coil spring forcing said movable-escutcheon plate into sealing relationship with said stationary escutcheon plate; said stationary escutcheon plate having a cylindrical platform for seating said handle and a spherical protrusion having an opening permitting visual access to said visual indicator; said visual indicator having an indication at one end and being pivoted at the other end thereof so that said indication moves in a circular path.

5. An escutcheon unit for circuit breakers comprising a movable gas-excluding rigid escutcheon plate, a stationary escutcheon plate, a visual indicator, a handle and a driving mechanism and an aligning unit; said aligning unit resiliently pressing said movable escutcheon plate in-to sealing relationship with said stationary escutcheon plate; said visual indicator being moved by said driving mechanism when said circuit breaker is opened or closed; said stationary escutcheon plate being fixed with respect to said circuit breaker and having movably mounted thereon said handle which manually operates said circuit breaker.

6. An escutcheon unit for circuit breakers comprising a movable gas-excluding rigid escutcheon plate, a stationary escutcheon plate, a visual indicator, a handle and a driving mechanism and an aligning unit; said aligning unit resiliently pressing said movable escutcheon plate against said stationary escutcheon'plate;'said visual indicator being moved by said driving mechanism when said circuit breaker is opened or closed; said stationary escutcheon plate being fixed with respect to said circuit breaker and having movably mounted thereon said handle which manually operates said circuit breaker; said movable escutcheon plate resiliently pressed into sealing relationship with said stationary escutcheon plate; said stationary escutcheon plate having a cylindrical platform for seating said handle and a spherical protrusion having an opening permitting visual access to said visual indicator.

7. An escutcheon unit for circuit breakers comprising a movable gas-excluding rigid escutcheon plate, a stationary escutcheon plate, a visual indicator, a handle, a driving mechanism; said visual indicator having an indication at one end and being pivoted at the other end thereof so that said indication moves in a circular path; said driving mechanism being activated when said circuit breaker is opened or closed and comprising a sliding member, a spring and a link; said link being directly moved when said circuit breaker is opened or closed and rotatively attached to said slidable member; said spring being fixed at one end to said slidable member and at the other end thereof to said visual indicator.

References Cited in the file of this patent UNITED STATES PATENTS 919,563 Eveleth Apr. 27, 1909 969,581 Webster Sept. 6, 1910 1,558,982 Hane Oct. 27, 1925 1,860,054 Roller May 24, 1932 2,095,222 Wilms Oct. 5, 1937 2,158,317 Allen May 16, 1939 2,211,819 Innis Aug. 20, 1940 2,231,072 Jackson Feb. 11, 1941 2,322,301. Lindstrom et al. June 22, 1943 2,333,547 Neumann Nov. 2, 1943 2,348,228 Scott May 9, 1944 2,388,934 Pearson W Nov. 13, 1945 2,472,961 Scott June 14, 1949 FOREIGN PATENTS 302,144 Germany Dec. 3, 1917 708,974 Germany Aug. 2, 1941 

